US20070051930A1 - Near-infrared-absorbing glass, near-infrared-absorbing element having the same and image-sensing device - Google Patents
Near-infrared-absorbing glass, near-infrared-absorbing element having the same and image-sensing device Download PDFInfo
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- US20070051930A1 US20070051930A1 US11/516,047 US51604706A US2007051930A1 US 20070051930 A1 US20070051930 A1 US 20070051930A1 US 51604706 A US51604706 A US 51604706A US 2007051930 A1 US2007051930 A1 US 2007051930A1
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- infrared
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- absorbing
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- 239000011521 glass Substances 0.000 title claims abstract description 161
- 238000002834 transmittance Methods 0.000 claims abstract description 64
- 125000002091 cationic group Chemical group 0.000 claims abstract description 16
- 125000000129 anionic group Chemical group 0.000 claims abstract description 15
- 238000000034 method Methods 0.000 claims description 22
- 238000000465 moulding Methods 0.000 claims description 19
- 230000003287 optical effect Effects 0.000 claims description 18
- 230000008569 process Effects 0.000 claims description 17
- 239000002994 raw material Substances 0.000 claims description 17
- 239000004065 semiconductor Substances 0.000 claims description 14
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 238000002844 melting Methods 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 8
- 230000003595 spectral effect Effects 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 6
- 150000002222 fluorine compounds Chemical class 0.000 claims description 2
- 238000010521 absorption reaction Methods 0.000 abstract description 19
- 238000004031 devitrification Methods 0.000 description 15
- 241000282326 Felis catus Species 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 8
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000011737 fluorine Substances 0.000 description 7
- 229910052731 fluorine Inorganic materials 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 230000035945 sensitivity Effects 0.000 description 7
- 239000005303 fluorophosphate glass Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000005304 optical glass Substances 0.000 description 6
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 5
- 239000010453 quartz Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 4
- -1 carbonate compound Chemical class 0.000 description 4
- 238000005266 casting Methods 0.000 description 4
- 230000005499 meniscus Effects 0.000 description 4
- 239000006060 molten glass Substances 0.000 description 4
- 238000007493 shaping process Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 3
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 3
- 229910019142 PO4 Inorganic materials 0.000 description 3
- 230000000903 blocking effect Effects 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
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- 239000000156 glass melt Substances 0.000 description 3
- 230000009477 glass transition Effects 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 235000021317 phosphate Nutrition 0.000 description 3
- 239000005365 phosphate glass Substances 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- 238000004383 yellowing Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 238000012937 correction Methods 0.000 description 2
- 239000005357 flat glass Substances 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 229910001260 Pt alloy Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 230000032900 absorption of visible light Effects 0.000 description 1
- 229910001413 alkali metal ion Inorganic materials 0.000 description 1
- 229910001420 alkaline earth metal ion Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- TXKMVPPZCYKFAC-UHFFFAOYSA-N disulfur monoxide Inorganic materials O=S=S TXKMVPPZCYKFAC-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical compound S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000000930 thermomechanical effect Effects 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/12—Silica-free oxide glass compositions
- C03C3/23—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron
- C03C3/247—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron containing fluorine and phosphorus
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C4/00—Compositions for glass with special properties
- C03C4/08—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths
- C03C4/082—Compositions for glass with special properties for glass selectively absorbing radiation of specified wave lengths for infrared absorbing glass
Definitions
- the present invention relates to a near-infrared-absorbing glass, a near-infrared-absorbing element having the same, a process for the production of the element and an image-sensing device. More specifically, the present invention relates to a near-infrared-absorbing glass suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter for correcting the color sensitivity of an image-sensing device such as CCD or CMOS for use particularly in a digital camera, a VTR camera or the like, a near-infrared-absorbing element as is described above, a process for efficiently producing the element and an image-sensing apparatus having the near-infrared-absorbing element.
- a near-infrared-absorbing glass suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter for correcting the color sensitivity of an image-sensing device such as CCD or CMOS for use particularly in a
- a solid image-sensing device such as CCD or the like for use in a digital camera or a VTR camera has a spectral sensitivity ranging from a visible light region to about 1,100 nm.
- a filter that absorbs light in a near infrared region is used to obtain an image close to an image of luminosity factor to human eyes.
- As a glass for this purpose there has been used a glass obtained by adding CuO to a phosphate glass.
- the phosphate glass has poor climate resistance, and there is a defect that the phosphate glass causes surface roughening or opacification when exposed to high temperatures and high humidity for a long period of time.
- a fluorine-component-containing near-infrared-absorbing filter glass that has the basic composition containing a fluorophosphate glass excellent in climate resistance, and such a glass is commercially available.
- a near-infrared-absorbing filter glass obtained by adding Cu to a fluorophosphate glass (for example, see JP-A-2-204342).
- a near-infrared-absorbing filter formed from a conventional Cu-containing fluorophosphate glass has no sufficient absorption at a wavelength of 1,000 to 1,200 nm, it is required to form a multi-layered film for infra red absorption by a method of vapor deposition, sputtering or the like. It has been hence difficult to provide near-infrared-absorbing filters at a low cost due to a coating cost.
- a near-infrared-absorbing filter glass disclosed in the above JP-A-2-204342 has a large aluminum element content as shown in Examples, and the absorption at a wavelength of 1,000 to 1,200 nm is not necessarily sufficient.
- a carbonate compound, a nitrate compound, a hydroxide, etc. are used as raw materials to make it easier to dissolve and refine the glass, and Cu is rendered divalent with a gas generated by decomposition of the raw materials in order to realize a high transmittance.
- the carbonate compound, nitrate compound, hydroxide, etc. are decomposed to generate a gas. Further, the volatilization of fluorine is also promoted together with the gas, so that it is said that the dissolving of a glass of the above type involves a large environmental load. Further, it is difficult to control the volatilization of fluorine since the volume of the discharge gas is large, and it has been hence difficult to produce a glass having a large fluorine content.
- the present inventor has made diligent studies, and as a result, it has been found that a glass having specific contents of specific cationic and anionic components is suitable as a near-infrared-absorbing glass for the above object.
- a near-infrared-absorbing element can be efficiently obtained by heating and precision press-molding a preform formed of the above near-infrared-absorbing glass.
- the present invention has been accordingly completed on the basis of the above finding.
- the present invention provides
- a near-infrared-absorbing glass comprising, by cationic %, 25 to 45% of P 5+ , 1 to 10% of Al 3+ , 15 to 30% of Li + , 0.1 to 10% of Mg 2+ , 0.1 to 20% of Ca 2+ , 0.1 to 20% of Sr 2+ , 0.1 to 20 Ba 2+ and 1 to 8% of Cu 2+ and comprising, as anionic components, 25 to 50 anionic % of F ⁇ and O 2 ⁇ ,
- a near-infrared-absorbing glass as recited in any one of the above (1) to (4), which has a transmittance property represented by a transmittance of less than 15% at a wavelength of 1,200 nm when it is thickness-adjusted such that it exhibits a transmittance of 50% at a wavelength of 615 nm in a spectral transmittance at a wavelength of 500 to 700 nm,
- a near-infrared-absorbing element as recited in the above (8), which is a near-infrared-absorbing filter having a glass plate formed of a near-infrared-absorbing glass,
- an image-sensing apparatus comprising the near-infrared-absorbing element recited in the above (8) and a semiconductor image-sensing device for receiving light to be transmitted through it, and
- an image-sensing apparatus comprising the near-infrared-absorbing element produced by the process recited in the above (12) and a semiconductor image-sensing device for receiving light to be transmitted through it.
- a near-infrared-absorbing glass that has excellently high transmittance in a visible light region, an excellent near-infrared-absorbing property and excellent climate resistance and that is suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter, a near-infrared-absorbing element as is described above, a process for efficiently producing the element and an image-sensing apparatus having the above near-infrared-absorbing element.
- FIG. 1 is a chart showing spectral transmittances of near-infrared-absorbing glasses obtained in Example 1 and Comparative Example 1.
- the near-infrared-absorbing glass of the present invention will be explained with regard to its transmittance property.
- the near-infrared-absorbing glass of the present invention when the near-infrared-absorbing glass has such a thickness that it exhibits a transmittance of 50% at a wavelength of 615 nm in a spectral transmittance at a wavelength of 500 to 700 nm, the transmittance thereof at a wavelength of 1,200 nm is less than 15%, preferably 13% or less. In a more preferred embodiment, not only the near-infrared-absorbing glass exhibits the above property, but also it exhibits the property represented by
- the transmittance as used herein refers to a value obtained by providing a glass sample having two optically polished flat surfaces that are in parallel with each other, causing light to enter the glass sample through one of the flat surfaces at right angles with the flat surface and dividing the intensity of light that comes out through the other of the above two flat surfaces with the intensity that the light has before caused to enter the sample. This transmittance is also called “external transmittance”.
- the color sensitivity of a semiconductor image-sensing device such as CCD, CMOS or the like for use in a digital camera or a VTR camera can be corrected.
- the absorption of near-infrared light at a wavelength of 700 to 1,200 nm is increased, so that the color sensitivity of a semiconductor image-sensing device can be excellently corrected without providing a near-infrared-blocking multi-layered film and that excellent color reproduction can be hence realized as an image sensing apparatus.
- the raw materials are limited to only solid oxide raw materials including a phosphate raw material and a solid fluoride raw material, and the process uses none of a carbonate, a nitrate, a sulfate, a hydroxide, a hydrate, an aqueous solution and the like.
- discharge gas emitted during melting can be controlled so that the amount thereof is small and the environmental load is decreased.
- the volatilization of fluorine is suppressed and a glass having a large content of fluorine can be melted. Further, the contamination and damage of a furnace or an ambient atmosphere by the volatilization of fluorine can be suppressed, so that the glass can be efficiently produced.
- a percentage for a content of a cationic component or a total content of cationic components hereinafter represents cationic %
- a percentage for a content of an anionic component hereinafter represents anionic % unless otherwise specified.
- a content ratio of cationic components is based cationic %.
- the near-infrared-absorbing glass of the present invention comprises, by cationic %, 25 to 45% of P 5+ , 1 to 10% of Al 3+ , 15 to 30% of Li + , 0.1 to 10% of Mg 2+ , 0.1 to 20% of Ca 2+ , 0.1 to 20% of Sr 2+ , 0.1 to 20 Ba 2+ and 1 to 8% of Cu 2+ and comprises, as anionic components, 25 to 50 anionic % of F ⁇ and O 2 ⁇ .
- P 5+ is a basic component of the fluorophosphate glass and is an essential component that brings the absorption by Cu 2+ in an infra red region.
- the content of P 5+ is therefore limited to 25 to 45%, and it is preferably 30 to 40%.
- Al 3+ is an essential component that improves the fluorophosphate glass in devitrification resistance, heat resistance, thermal impact resistance, mechanical strength and chemical durability.
- the content of Al 3+ is therefore limited to 1 to 10%. It is preferably 2 to 8%, more preferably 2 to 7%.
- the ratio of content of Al 3+ to the content of P 5+ , Al 3+ /P 5+ is an important factor for satisfying both absorption in a near infrared region and transmission in a visible light region.
- the above ratio is less than 0.05, the durability tends to be poor.
- it exceeds 0.30 the absorption in the near infrared region is small, and the transmission of visible light tends to decrease.
- the above ratio (Al 3+ /P 5+ ) is therefore preferably adjusted in the range of 0.05 to 0.30, more preferably in the range of 0.05 to 0.25, still more preferably in the range of 0.05 to 0.20.
- Li + is an essential component for improving the glass in meltability, devitrification resistance and transmittance in a visible light region.
- the content of Li + is therefore limited to 15 to 30%. It is preferably 17 to 30%, more preferably 20 to 30%.
- Mg2+ is an essential component that improves the glass in devitrification resistance, durability and processability.
- the content of Mg 2+ is therefore limited to 0.1 to 10%, and it is preferably 1 to 9%, more preferably 1 to 8%.
- Ca 2+ is a useful component that improves the glass in devitrification resistance, durability and processability.
- the content of Ca 2+ is therefore limited to 0.1 to 20%, and it is preferably 5 to 15%.
- Sr 2+ is a useful component that improves the glass in devitrification resistance and meltability.
- the content of Sr 2+ is therefore limited to 0.1 to 20%, and it is preferably 1 to 10%.
- Ba 2+ is a useful component that improves the glass in devitrification resistance and meltability.
- the content of Ba 2+ is therefore limited to 0.1 to 20%, and it is preferably 1 to 10%.
- the ratio of the total content of Mg 2+ and Ca 2+ to the total content of Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ , (Mg 2+ +Ca 2+ )/(Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ ), is less than 0.5, the glass is liable to be poor in devitrification resistance, durability and processability and the specific gravity thereof tends to increase. It is therefore preferred to the above ratio of (Mg 2+ +Ca 2+ )/(Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ ) in the range of 0.5 to less than 1.0.
- the content of Cu 2+ is therefore limited to 1 to 8%. It is preferably 2 to 7%.
- F ⁇ is an essential anionic component that decreases the melting point of the glass and improves the glass in climate resistance.
- the melting temperature of the glass is decreased, the reduction of Cu 2+ is suppressed and predetermined optical properties can be obtained.
- the content of F ⁇ is less than 25%, the climate resistance is degraded.
- it exceeds 50% the content of O 2 ⁇ is relatively decreased, so that coloring occurs at and around 400 nm due to monovalent Cu + .
- the content of F ⁇ is therefore limited to 25 to 50%, and it is preferably 30 to 45%.
- O 2 ⁇ is a particularly important anionic component for the near-infrared-absorbing glass of the present invention, and in a preferred embodiment, the entirety of the anionic portion excluding F ⁇ in the glass is constituted of an O 2 ⁇ component.
- the content of O 2 ⁇ is less than 50%, divalent Cu 2+ is reduced to monovalent Cu + , so that the absorption in a short wavelength region, in particular at and around 400 nm, is large, which leads a color to be greenish.
- it exceeds 75% the glass has a high viscosity and has a high melting temperature, so that the transmittance is liable to be degraded.
- the content of O 2 ⁇ is preferably 50 to 75%, more preferably 55 to 70%.
- the glass of the present invention may contain a small amount of other anionic components such as Cl ⁇ , Br ⁇ , I ⁇ , etc., together with the above F ⁇ and O 2 ⁇ .
- Na + , K + and Zn 2+ have an effect on improvements of the meltability and devitrification resistance, they impair the near-infrared-absorbing property, so that it is desirable to add none of these.
- the ratio of content of Li + of alkali metal ions is to be increased, and it is preferred to adjust the ratio of content of Li + to the total content of Li + , Na + and K + , Li + /(Li + +Na + +K + ), to 0.8 to 1.0, and it is more preferred to adjust the above ratio to 0.9 to 1.0.
- Pb is very harmful, and it is hence desirable to use no Pb in the present invention.
- Sb also has an effect on improvement of transmittance, but for the same reason, it is preferred to use no Sb.
- raw materials in the form of a solid powder are used as glass raw materials as described above.
- oxides including anhydrous phosphate and a fluoride raw material are prepared as required, these raw materials are weighed so as to obtain a desired composition and mixed, and the mixture is then melted in a refractory crucible at approximately 800 to 900° C.
- a refractory cover of platinum or the like for suppressing the volatilization of a fluorine component, it is desirable to use a refractory cover of platinum or the like.
- a glass in a molten state is stirred and refined and then the glass is caused to flow out for molding (shaping).
- a method for molding (shaping) the glass there can be employed a known method such as a casting, pipe-flowing, rolling or pressing method.
- the near-infrared-absorbing glass of the present invention is excellent in climate resistance. For use for a long period of time, the glass is required to have excellent climate resistance. When the climate resistance is low, fogging occurs on the glass surface, and the glass is no longer usable in the field of a near-infrared-absorbing element and the like.
- the climate resistance as used herein is tested by holding an optically polished glass sample under conditions including a temperature of 60° C. and a relative humidity of 80% for 1,000 hours and then visually observing the optically polished surface of the sample for a yellowing state. As a result, when no yellowing state is observed, it can be confirmed that such a glass has climate resistance sufficient for use for a long period of time. With regard to the near-infrared-absorbing glass of the present invention, it has been confirmed that no yellowing state is observed in the test under the above conditions and that the near-infrared-absorbing glass of the present invention hence has excellent climate resistance.
- the near-infrared-absorbing element of the present invention has the above near-infrared-absorbing glass or a near-infrared-absorbing glass produced by the above process.
- the near-infrared-absorbing element of the present invention may be a near-infrared-absorbing element a part of which uses the above near-infrared-absorbing glass, such as an element in which a glass plate formed of the near-infrared-absorbing glass is attached to a quartz plate, or a near-infrared-absorbing element which is entirely formed of the near-infrared-absorbing glass.
- the above glass plate formed of the near-infrared-absorbing glass is produced as follows.
- a refined and homogenized molten glass is cast from a pipe into a casting mold and shaped into a glass block having a large thickness and a large size.
- a casting mold that is constituted of a flat and horizontal bottom surface, a pair of side walls in parallel with each other across the bottom surface and a blocking plate positioned from one side wall to the other side wall to close one opening, and a homogenized molten glass is cast into the above mold from a pipe made of a platinum alloy at a constant flow rate.
- a cast molten glass spreads in the mold to be shaped into a plate-shaped glass, which is defined by the pair of side walls to have a constant width.
- the thus-shaped plate-shaped glass is continuously withdrawn from the opening portion of the mold.
- molding (shaping) conditions such as the form and dimensions of the mold, the flow rate of the molten glass, etc., are determined as required, whereby there can be formed a glass block having a large size and a large thickness.
- the thus-shaped glass block is transferred into an annealing furnace, which is pre-heated to a temperature around the transition temperature of the glass, and gradually cooled to room temperature.
- the glass block that has been gradually cooled to remove a strain is subjected to accurate slicing, grinding and polishing, whereby glass plate(s) having both surfaces optically polished can be obtained.
- a near-infrared-absorbing glass that is the above glass plate
- a plate-shaped optical glass that transmits visible light and that has both surfaces optically polished such as BK-7 (borosilicate optical glass) is attached to the other surface of the quartz plate.
- BK-7 borosilicate optical glass
- the near-infrared-absorbing filter is constituted to have the above structure
- one more plate-shaped optical glass that transmits visible light and that has both surfaces optically polished e.g., BK-7) may be attached to the other surface of the above plate-shaped optical glass.
- An optical multi-layered film may be formed on the filter surface as required.
- the glass block may be ground and polished to produce a lens or may be processed to produce a product having other form.
- optical elements such as a lens, a diffraction grating, etc. can be produced therefrom by precision press-molding (mold-shaping) without using any machine-applied processing such as grinding and polishing of their optical-function surfaces.
- molding surfaces of a known press mold material such as SiC, a carbide material or the like are highly accurately processed so that they have reverse forms of lens surfaces of an aspherical lens, whereby upper and lower mold members are prepared, and a glass preform formed of the near-infrared-absorbing glass of the present invention is heated and precision press-molded with these upper and lower mold members and optionally with a known sleeve or upper and lower mold guide member(s).
- the forms of the molding surfaces are accurately transferred to the glass in the above manner, whereby an aspherical lens formed of the near-infrared-absorbing glass of the present invention can be produced.
- the thus-obtained aspherical lens is a near-infrared-absorbing element having the function of near infrared absorption and can constitute part or the whole of an optical system for forming an image of an object on a semiconductor image-sensing device, so that the number of optical parts in an image-sensing apparatus can be decreased and that space saving and cost reduction can be realized at the same time.
- Molding surfaces of a press mold material are highly accurately processed so that they have reverse forms of a diffraction grating to prepare upper and lower mold members, and a glass preform is precision press-molded with the above mold in the same manner as in the above-described method, whereby a diffraction grating formed of the near-infrared-absorbing glass of the present invention can be also produced.
- the thus-obtained near-infrared-absorbing element with a diffraction grating works as an optical low-pass filter for light that enters a semiconductor image-sensing device. Since a near-infrared-absorbing filter and an optical low-pass filter can be therefore constituted of one element, the number of optical parts in an image-sensing apparatus can be decreased, and space saving and cost reduction can be realized at the same time.
- molding surfaces of a press mold material are formed in a reverse form of lens surfaces (e.g., lens surfaces of an aspherical lens) and at the same time processed in a reverse form of grooves of a diffraction grating, and precision press-molding is carried out in the same manner as in the above method, whereby there can be produced a near-infrared-absorbing element that has the function of near infrared absorption, the function of an optical low-pass filter and the function of a lens together.
- lens surfaces e.g., lens surfaces of an aspherical lens
- a known mold release film may be formed on the molding surface(s) of a press mold as required.
- Various conditions of the precision press-molding can be determined as required depending upon specifications of an intended near-infrared-absorbing element while applying known conditions.
- near-infrared-absorbing elements By producing near-infrared-absorbing elements according to the above precision press-molding, there can be highly productively produced elements for which mass-production by grinding and polishing is not suitable, such as an aspherical lens, an optical low-pass filter with a diffraction grating, an aspherical lens that functions as an optical low-pass filter and has a diffraction grating, and the like.
- An optical multi-layered film such as an anti-reflection film may be formed on the surface of a near-infrared-absorbing element as required.
- the transmittance of visible light is high, and the absorption of near infrared light is large, so that the color sensitivity of a semiconductor image-sensing device can be excellently corrected.
- the present invention also provides an image-sensing apparatus having the above near-infrared-absorbing element and a semiconductor image-sensing device for receiving light that passes through the element and an image-sensing apparatus having a near-infrared-absorbing element produced by the above production process and a semiconductor image-sensing device for receiving light that passes through the element.
- Oxide materials including phosphates and fluoride materials were weighed so as to obtain a composition shown in Table 1, and they were mixed and melted in a crucible made of platinum. Glasses in Examples 1 to 6 were melted at 800 to 900° C., and a glass in Comparative Example 1 was melted at 1,300° C.
- Each glass was stirred and refined, and then it was cast on an iron plate to form a block.
- the glass block was transferred into a furnace, which was pre-heated to a temperature around a glass transition temperature, and annealed to room temperature to give near-infrared-absorbing glasses.
- a glass that was polished and had a thickness shown in Table 1 was measured for spectral transmittances at a wavelength of 200 to 1,200 with a spectrophotometer. Table 1 shows a transmittance at each wavelength.
- a polished sample was held under conditions including a temperature of 60° C. and a relative humidity of 80% for 1,000 hours and then the surface was observed for an opacification or fogging.
- Tg Transition Temperature
- Ts sag Temperature
- FIG. 1 shows spectral transmittances of glasses of Example 1 and Comparative Example 1.
- Spectral transmittances were obtained when the thickness of each of the glass of Example 1 and the glass of Comparative Example 1 was adjusted such the transmittance at a wavelength of 615 nm was 50%, that is, the glasses of Example 1 and Comparative Example 1 had thicknesses as shown in Table 1.
- the glass of Example 1 has sufficient transmittance to visible light and sufficient absorption of near infrared light and has a transmittance property that the color sensitivity of a semiconductor image-sensing device can be excellently corrected without forming a near infrared blocking coating.
- the glass of Comparative Example 1 has low near infrared absorption function, so that its property is that it is desirable to form a near infrared blocking coating for completing the color correction function of a semiconductor image-sensing device.
- near-infrared-absorbing glasses having a glass transition temperature of less than 400° C., a sag temperature of less than 450° C. and an average linear expansion coefficient, measured at 100 to 300° C., of greater than 130 ⁇ 10 ⁇ 7 /° C. but smaller than 180 ⁇ 10 ⁇ 7 /° C.
- Plate-shaped glasses formed of glasses having the same compositions as those in Examples 1 to 6 were obtained (molded) by carrying out glass dissolving, refining, homogenizing and mold-casting in the same manner as in Examples 1 to 6.
- Each plate-shaped glass was sliced and both surfaces of each of the sliced glasses were optically polished to obtain glass plates having predetermined thicknesses.
- These glass plates were dice-processed to give near-infrared-absorbing glass plates having predetermined thicknesses and sizes.
- the thickness of each of the glass plates was adjusted such that the transmittance at a wavelength of 615 ⁇ 10 nm was 50% (thicknesses corresponding to measurement thicknesses in Table 1), and each glass plate had a size of 10 mm ⁇ 10 mm to 30 mm ⁇ 30 mm.
- Images were taken by arranging the above element in front of the light receiving surface of a semiconductor image-sensing device such as CCD, CMOS or the like. Images taken by the above arrangement using the elements of this Example were observed to show that excellent color correction was attained.
- a glass melt was prepared by melting, refining and homogenizing a glass in the same manner as in Examples 1 to 6, and the glass melt was caused to flow down from a nozzle made of platinum.
- a proper amount of the glass melt was received with a receiving mold and shaped into a spherical glass preform.
- the thus-shaped preform was once cooled to room temperature and in a non-oxidizing atmosphere containing nitrogen gas or a mixture of nitrogen with hydrogen, the preform was again softened by re-heating and pressed with a press mold.
- the molding surfaces of the press mold were accurately processed in advance in a reverse form of an intended optical element, and the forms of these molding surfaces were accurately transferred to the glass in the above pressing step.
- the press-molded product was cooled in the press mold to a temperature at which the glass was not deformed, and then it was taken out from the press mold and annealed.
- a spherical glass preform may be produced by preparing a glass block formed of the glass of any one of Example 1 to 6 in the same manner as in Example 7.
- an optical element such as an aspherical lens or a diffraction grating or a near-infrared-absorbing element having a diffraction grating on a surface may be produced by precision press-molding in the same manner as in the above.
- the form of a lens there can be produced lenses with various forms such as a convex meniscus form, a concave meniscus form, a biconvex form, a biconcave form, a plano-convex form, a plano-concave form and the like.
- a convex meniscus form a concave meniscus form
- a biconvex form a biconcave form
- a plano-convex form a plano-concave form and the like.
- the lens form is preferably a convex meniscus form or a concave meniscus form.
- the near-infrared-absorbing glass of the present invention has excellently high transmittance in a visible light region, an excellent near infrared absorption property, excellent climate resistance, etc., and is suitable for use as/in a near-infrared-absorbing element such as a near-infrared-absorbing filter. Further, the above near-infrared-absorbing filter is particularly suitably used for correcting the color sensitivity of an image-sensing device of CCD, CMOS or the like used in a digital camera or VTR camera.
Abstract
Provided are a near-infrared-absorbing glass having high transmittance in a visible light region, an excellent near infrared absorption property, excellent climate resistance, etc., and is suitable for use as/in a near-infrared-absorbing element such as a near-infrared-absorbing filter, and a near-infrared-absorbing element to which the above near-infrared-absorbing glass is applied, and the near-infrared-absorbing glass contains, by cationic %, 25 to 45% of P5+, 1 to 10% of Al3+, 15 to 30% of Li+, 0.1 to 10% of Mg2+, 0.1 to 20% of Ca2+, 0.1 to 20% of Sr2+, 0.1 to 20 Ba2+ and 1 to 8% of Cu2+ and contains, as anionic components, 25 to 50 anionic % of F− and O2−.
Description
- The present invention relates to a near-infrared-absorbing glass, a near-infrared-absorbing element having the same, a process for the production of the element and an image-sensing device. More specifically, the present invention relates to a near-infrared-absorbing glass suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter for correcting the color sensitivity of an image-sensing device such as CCD or CMOS for use particularly in a digital camera, a VTR camera or the like, a near-infrared-absorbing element as is described above, a process for efficiently producing the element and an image-sensing apparatus having the near-infrared-absorbing element.
- A solid image-sensing device such as CCD or the like for use in a digital camera or a VTR camera has a spectral sensitivity ranging from a visible light region to about 1,100 nm. A filter that absorbs light in a near infrared region is used to obtain an image close to an image of luminosity factor to human eyes. As a glass for this purpose, there has been used a glass obtained by adding CuO to a phosphate glass. However, the phosphate glass has poor climate resistance, and there is a defect that the phosphate glass causes surface roughening or opacification when exposed to high temperatures and high humidity for a long period of time. There has been hence developed a fluorine-component-containing near-infrared-absorbing filter glass that has the basic composition containing a fluorophosphate glass excellent in climate resistance, and such a glass is commercially available.
- As a glass of the above type, for example, there has been disclosed a near-infrared-absorbing filter glass obtained by adding Cu to a fluorophosphate glass (for example, see JP-A-2-204342).
- Since, however, a near-infrared-absorbing filter formed from a conventional Cu-containing fluorophosphate glass has no sufficient absorption at a wavelength of 1,000 to 1,200 nm, it is required to form a multi-layered film for infra red absorption by a method of vapor deposition, sputtering or the like. It has been hence difficult to provide near-infrared-absorbing filters at a low cost due to a coating cost.
- A near-infrared-absorbing filter glass disclosed in the above JP-A-2-204342 has a large aluminum element content as shown in Examples, and the absorption at a wavelength of 1,000 to 1,200 nm is not necessarily sufficient.
- In recent years, further, it is required to decrease an environmental load with regard to glass production, and gas generated during the melting of a glass is brought into question in many cases. In particular, there are legal controls imposed on nitrogen oxide, sulfur oxide and other air contaminants, and it is required to arrange that they are not discharged into atmosphere. Generally, they are rendered harmless in gas treatment facilities of a large scale and then discharged. However, the maintenance and management of such facilities require a very large cost.
- In a near-infrared-absorbing filter formed of a conventional Cu-containing fluorophosphate glass, a carbonate compound, a nitrate compound, a hydroxide, etc., are used as raw materials to make it easier to dissolve and refine the glass, and Cu is rendered divalent with a gas generated by decomposition of the raw materials in order to realize a high transmittance. When raw materials for the glass are dissolved, however, the carbonate compound, nitrate compound, hydroxide, etc., are decomposed to generate a gas. Further, the volatilization of fluorine is also promoted together with the gas, so that it is said that the dissolving of a glass of the above type involves a large environmental load. Further, it is difficult to control the volatilization of fluorine since the volume of the discharge gas is large, and it has been hence difficult to produce a glass having a large fluorine content.
- Problems to be Solved by the Invention
- Under the circumstances, it is an object of the present invention to provide a near-infrared-absorbing glass that has excellent transmittance in a visible light region, excellent absorption in a near infrared region and excellent climate resistance and that is suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter, a near-infrared-absorbing element as is described above, a process for efficiently producing the element and an image-sensing device having the above near-infrared-absorbing element.
- Means to Solve the Problems
- For achieving the above object, the present inventor has made diligent studies, and as a result, it has been found that a glass having specific contents of specific cationic and anionic components is suitable as a near-infrared-absorbing glass for the above object.
- Further, it has been found that a near-infrared-absorbing element can be efficiently obtained by heating and precision press-molding a preform formed of the above near-infrared-absorbing glass.
- The present invention has been accordingly completed on the basis of the above finding.
- That is, the present invention provides
- (1) a near-infrared-absorbing glass comprising, by cationic %, 25 to 45% of P5+, 1 to 10% of Al3+, 15 to 30% of Li+, 0.1 to 10% of Mg2+, 0.1 to 20% of Ca2+, 0.1 to 20% of Sr2+, 0.1 to 20 Ba2+ and 1 to 8% of Cu2+ and comprising, as anionic components, 25 to 50 anionic % of F− and O2−,
- (2) a near-infrared-absorbing glass as recited in the above (1), wherein the ratio of the content of Al3+ to the content of p5+ by cationic ratio, Al3+/P5+, is from 0.05 to 0.30,
- (3) a near-infrared-absorbing glass as recited in the above (1) or (2), wherein the ratio of the total content of Mg2+ and Ca2+ to the total content of Mg2+, Ca2+, Sr2+ and Ba2+ by cationic ratio, (Mg2++Ca2+)/(Mg2++Ca2++Sr2++Ba2+), is from 0.5 to less than 1.0,
- (4) a near-infrared-absorbing glass as recited in any one of the above (1) to (3), wherein the ratio of the content of Li+ to the total content of Li+, Na+ and K+ by cationic ratio, Li+/(Li++Na++K+), is from 0.8 to 1.0,
- (5) a near-infrared-absorbing glass as recited in any one of the above (1) to (4), which has a transmittance property represented by a transmittance of less than 15% at a wavelength of 1,200 nm when it is thickness-adjusted such that it exhibits a transmittance of 50% at a wavelength of 615 nm in a spectral transmittance at a wavelength of 500 to 700 nm,
- (6) a near-infrared-absorbing glass as recited in the above (5), which further has the transmittance property represented by
- a transmittance of 83% or more at a wavelength of 400 nm,
- a transmittance of 88% or more at a wavelength of 500 nm,
- a transmittance of 55% or more at a wavelength of 600 nm,
- a transmittance of less than 8% at a wavelength of 700 nm,
- a transmittance of less than 1% at a wavelength of 800 nm,
- a transmittance of less than 1% at a wavelength of 900 nm,
- a transmittance of less than 3% at a wavelength of 1,000 nm, and
- a transmittance of less than 7% at a wavelength of 1,100 nm,
- (7) a process for the production of the near-infrared-absorbing glass recited in any one of the above (1) to (6), which comprises providing only solid oxides and fluorides as raw materials, heating and melting said raw materials and forming the glass,
- (8) A near-infrared-absorbing element having the near-infrared-absorbing glass recited in any one of the above (1) to (6) or the near-infrared-absorbing glass produced by the process recited in the above (7),
- (9) a near-infrared-absorbing element as recited in the above (8), which is a near-infrared-absorbing filter having a glass plate formed of a near-infrared-absorbing glass,
- (10) a near-infrared-absorbing element as recited in the above (8) or (9), which is an optical low-pass filter,
- (11) a near-infrared-absorbing element as recited in the above (8) or (10), which is a lens,
- (12) a process for the production of a near-infrared-absorbing element, which comprises heating and precision press-molding a preform formed of the near-infrared-absorbing glass recited in any one of the above (1) to (6) or a near-infrared-absorbing glass produced by the process recited in the above (7),
- (13) an image-sensing apparatus comprising the near-infrared-absorbing element recited in the above (8) and a semiconductor image-sensing device for receiving light to be transmitted through it, and
- (14) an image-sensing apparatus comprising the near-infrared-absorbing element produced by the process recited in the above (12) and a semiconductor image-sensing device for receiving light to be transmitted through it.
- Effect of the Invention
- According to the present invention, there can be provided a near-infrared-absorbing glass that has excellently high transmittance in a visible light region, an excellent near-infrared-absorbing property and excellent climate resistance and that is suitable for a near-infrared-absorbing element such as a near-infrared-absorbing filter, a near-infrared-absorbing element as is described above, a process for efficiently producing the element and an image-sensing apparatus having the above near-infrared-absorbing element.
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FIG. 1 is a chart showing spectral transmittances of near-infrared-absorbing glasses obtained in Example 1 and Comparative Example 1. - First, the near-infrared-absorbing glass of the present invention will be explained with regard to its transmittance property.
- In a preferred embodiment of the near-infrared-absorbing glass of the present invention, when the near-infrared-absorbing glass has such a thickness that it exhibits a transmittance of 50% at a wavelength of 615 nm in a spectral transmittance at a wavelength of 500 to 700 nm, the transmittance thereof at a wavelength of 1,200 nm is less than 15%, preferably 13% or less. In a more preferred embodiment, not only the near-infrared-absorbing glass exhibits the above property, but also it exhibits the property represented by
- a transmittance of 83% or more, preferably 85% ore more, more preferably 87% or more, at a wavelength of 400 nm,
- a transmittance of 88% or more, preferably 89% or more, more preferably 90% or more, at a wavelength of 500 nm,
- a transmittance of 55% or more at a wavelength of 600 nm,
- a transmittance of less than 8% at a wavelength of 700 nm,
- a transmittance of less than 1% at a wavelength of 800 nm,
- a transmittance of less than 1% at a wavelength of 900 nm,
- a transmittance of less than 3%, preferably 2% or less, at a wavelength of 1,000 nm, and
- a transmittance of less than 7%, preferably 5% or less, at a wavelength of 1,100 nm.
- That is, the absorption of near infra red at a wavelength of 700 to 1,200 nm is large, and the absorption of visible light at a wavelength of 400 to 600 nm is small. The transmittance as used herein refers to a value obtained by providing a glass sample having two optically polished flat surfaces that are in parallel with each other, causing light to enter the glass sample through one of the flat surfaces at right angles with the flat surface and dividing the intensity of light that comes out through the other of the above two flat surfaces with the intensity that the light has before caused to enter the sample. This transmittance is also called “external transmittance”.
- Owing to the above transmittance property, the color sensitivity of a semiconductor image-sensing device such as CCD, CMOS or the like for use in a digital camera or a VTR camera can be corrected. In particular, the absorption of near-infrared light at a wavelength of 700 to 1,200 nm is increased, so that the color sensitivity of a semiconductor image-sensing device can be excellently corrected without providing a near-infrared-blocking multi-layered film and that excellent color reproduction can be hence realized as an image sensing apparatus.
- In the process for the production of a near-infrared-absorbing glass, provided by the present invention, only solid oxide and fluoride are used as raw materials, and the above raw materials are heated, melted and shaped (molded) to obtain a near-infrared-absorbing glass.
- Specifically, the raw materials are limited to only solid oxide raw materials including a phosphate raw material and a solid fluoride raw material, and the process uses none of a carbonate, a nitrate, a sulfate, a hydroxide, a hydrate, an aqueous solution and the like. In this manner, discharge gas emitted during melting can be controlled so that the amount thereof is small and the environmental load is decreased. At the same time the volatilization of fluorine is suppressed and a glass having a large content of fluorine can be melted. Further, the contamination and damage of a furnace or an ambient atmosphere by the volatilization of fluorine can be suppressed, so that the glass can be efficiently produced.
- The composition of the near-infrared-absorbing glass of the present invention will be explained below. A percentage for a content of a cationic component or a total content of cationic components hereinafter represents cationic %, and a percentage for a content of an anionic component hereinafter represents anionic % unless otherwise specified. Further, a content ratio of cationic components (including a ratio to a total content) is based cationic %.
- The near-infrared-absorbing glass of the present invention comprises, by cationic %, 25 to 45% of P5+, 1 to 10% of Al3+, 15 to 30% of Li+, 0.1 to 10% of Mg2+, 0.1 to 20% of Ca2+, 0.1 to 20% of Sr2+, 0.1 to 20 Ba2+ and 1 to 8% of Cu2+ and comprises, as anionic components, 25 to 50 anionic % of F− and O2−.
- P5+ is a basic component of the fluorophosphate glass and is an essential component that brings the absorption by Cu2+ in an infra red region. When the content of P5+ is less than 25%, a color transmitted through the glass is deteriorated and is greenish. When it exceeds 45%, the glass is degraded in climate resistance and devitrification resistance. The content of P5+ is therefore limited to 25 to 45%, and it is preferably 30 to 40%.
- Al3+ is an essential component that improves the fluorophosphate glass in devitrification resistance, heat resistance, thermal impact resistance, mechanical strength and chemical durability. When the content of Al3+ is less than 1%, none of these effects is produced, and when it exceeds 10%, the property of absorbing near infrared is degraded. The content of Al3+ is therefore limited to 1 to 10%. It is preferably 2 to 8%, more preferably 2 to 7%.
- In addition, the ratio of content of Al3+ to the content of P5+, Al3+/P5+, is an important factor for satisfying both absorption in a near infrared region and transmission in a visible light region. When the above ratio is less than 0.05, the durability tends to be poor. When it exceeds 0.30, the absorption in the near infrared region is small, and the transmission of visible light tends to decrease. The above ratio (Al3+/P5+) is therefore preferably adjusted in the range of 0.05 to 0.30, more preferably in the range of 0.05 to 0.25, still more preferably in the range of 0.05 to 0.20.
- Li+ is an essential component for improving the glass in meltability, devitrification resistance and transmittance in a visible light region. When the content of Li+ is less than 15%, such effects are not produced. When it exceeds 30%, the glass is degraded in durability and processability. The content of Li+ is therefore limited to 15 to 30%. It is preferably 17 to 30%, more preferably 20 to 30%.
- Mg2+ is an essential component that improves the glass in devitrification resistance, durability and processability. When the content of Mg2+ is less than 0.1%, such effects are not produced. When it exceeds 10%, the devitrification resistance is degraded. The content of Mg2+ is therefore limited to 0.1 to 10%, and it is preferably 1 to 9%, more preferably 1 to 8%.
- Ca2+ is a useful component that improves the glass in devitrification resistance, durability and processability. When the content of Ca2+ is less than 0.1%, such effects are not produced. When it exceeds 20%, the devitrification resistance is degraded. The content of Ca2+ is therefore limited to 0.1 to 20%, and it is preferably 5 to 15%.
- Sr2+ is a useful component that improves the glass in devitrification resistance and meltability. When the content of Sr2+ is less than 0.1%, no such effects are produced. When it exceeds 20%, the devitrification resistance is degraded. The content of Sr2+ is therefore limited to 0.1 to 20%, and it is preferably 1 to 10%.
- Ba2+ is a useful component that improves the glass in devitrification resistance and meltability. When the content of Ba2+ is less than 0.1%, no such effects are produced. When it exceeds 20%, the devitrification resistance is degraded. The content of Ba2+ is therefore limited to 0.1 to 20%, and it is preferably 1 to 10%.
- It has a significant influence on the devitrification resistance, durability, processability and specific gravity of the glass how alkaline earth metal ions are selected to incorporate them into the glass. That is, the ratio of the total content of Mg2+ and Ca2+ to the total content of Mg2+, Ca2+, Sr2+ and Ba2+, (Mg2++Ca2+)/(Mg2++Ca2++Sr2++Ba2+), is less than 0.5, the glass is liable to be poor in devitrification resistance, durability and processability and the specific gravity thereof tends to increase. It is therefore preferred to the above ratio of (Mg2++Ca2+)/(Mg2++Ca2++Sr2++Ba2+) in the range of 0.5 to less than 1.0.
- When the content of Cu2+ is less than 1%, the infrared absorption is small, and when it exceeds 8%, the devitrification resistance is degraded. The content of Cu2+ is therefore limited to 1 to 8%. It is preferably 2 to 7%.
- F− is an essential anionic component that decreases the melting point of the glass and improves the glass in climate resistance. In the glass of the present invention containing F−, the melting temperature of the glass is decreased, the reduction of Cu2+ is suppressed and predetermined optical properties can be obtained. When the content of F− is less than 25%, the climate resistance is degraded. When it exceeds 50%, the content of O2− is relatively decreased, so that coloring occurs at and around 400 nm due to monovalent Cu+. The content of F− is therefore limited to 25 to 50%, and it is preferably 30 to 45%.
- O2− is a particularly important anionic component for the near-infrared-absorbing glass of the present invention, and in a preferred embodiment, the entirety of the anionic portion excluding F− in the glass is constituted of an O2− component. When the content of O2− is less than 50%, divalent Cu2+ is reduced to monovalent Cu+, so that the absorption in a short wavelength region, in particular at and around 400 nm, is large, which leads a color to be greenish. When it exceeds 75%, the glass has a high viscosity and has a high melting temperature, so that the transmittance is liable to be degraded. The content of O2− is preferably 50 to 75%, more preferably 55 to 70%.
- The glass of the present invention may contain a small amount of other anionic components such as Cl−, Br−, I−, etc., together with the above F− and O2−.
- While Na+, K+ and Zn2+ have an effect on improvements of the meltability and devitrification resistance, they impair the near-infrared-absorbing property, so that it is desirable to add none of these.
- That is, the ratio of content of Li+ of alkali metal ions is to be increased, and it is preferred to adjust the ratio of content of Li+ to the total content of Li+, Na+ and K+, Li+/(Li++Na++K+), to 0.8 to 1.0, and it is more preferred to adjust the above ratio to 0.9 to 1.0.
- Pb is very harmful, and it is hence desirable to use no Pb in the present invention.
- Further, while As has an effect on improvement of transmittance, it is very harmful, so that it is desirable to use no As in the present invention. Sb also has an effect on improvement of transmittance, but for the same reason, it is preferred to use no Sb.
- In the production of the above near-infrared-absorbing glass, raw materials in the form of a solid powder are used as glass raw materials as described above. For example, only oxides including anhydrous phosphate and a fluoride raw material are prepared as required, these raw materials are weighed so as to obtain a desired composition and mixed, and the mixture is then melted in a refractory crucible at approximately 800 to 900° C. In this case, for suppressing the volatilization of a fluorine component, it is desirable to use a refractory cover of platinum or the like. A glass in a molten state is stirred and refined and then the glass is caused to flow out for molding (shaping).
- As a method for molding (shaping) the glass, there can be employed a known method such as a casting, pipe-flowing, rolling or pressing method.
- The near-infrared-absorbing glass of the present invention is excellent in climate resistance. For use for a long period of time, the glass is required to have excellent climate resistance. When the climate resistance is low, fogging occurs on the glass surface, and the glass is no longer usable in the field of a near-infrared-absorbing element and the like. The climate resistance as used herein is tested by holding an optically polished glass sample under conditions including a temperature of 60° C. and a relative humidity of 80% for 1,000 hours and then visually observing the optically polished surface of the sample for a yellowing state. As a result, when no yellowing state is observed, it can be confirmed that such a glass has climate resistance sufficient for use for a long period of time. With regard to the near-infrared-absorbing glass of the present invention, it has been confirmed that no yellowing state is observed in the test under the above conditions and that the near-infrared-absorbing glass of the present invention hence has excellent climate resistance.
- The near-infrared-absorbing element of the present invention has the above near-infrared-absorbing glass or a near-infrared-absorbing glass produced by the above process. The near-infrared-absorbing element of the present invention may be a near-infrared-absorbing element a part of which uses the above near-infrared-absorbing glass, such as an element in which a glass plate formed of the near-infrared-absorbing glass is attached to a quartz plate, or a near-infrared-absorbing element which is entirely formed of the near-infrared-absorbing glass.
- For example, the above glass plate formed of the near-infrared-absorbing glass is produced as follows.
- First, a refined and homogenized molten glass is cast from a pipe into a casting mold and shaped into a glass block having a large thickness and a large size. For example, there is prepared a casting mold that is constituted of a flat and horizontal bottom surface, a pair of side walls in parallel with each other across the bottom surface and a blocking plate positioned from one side wall to the other side wall to close one opening, and a homogenized molten glass is cast into the above mold from a pipe made of a platinum alloy at a constant flow rate. A cast molten glass spreads in the mold to be shaped into a plate-shaped glass, which is defined by the pair of side walls to have a constant width. The thus-shaped plate-shaped glass is continuously withdrawn from the opening portion of the mold. In this case, molding (shaping) conditions such as the form and dimensions of the mold, the flow rate of the molten glass, etc., are determined as required, whereby there can be formed a glass block having a large size and a large thickness.
- The thus-shaped glass block is transferred into an annealing furnace, which is pre-heated to a temperature around the transition temperature of the glass, and gradually cooled to room temperature. The glass block that has been gradually cooled to remove a strain is subjected to accurate slicing, grinding and polishing, whereby glass plate(s) having both surfaces optically polished can be obtained.
- When a near-infrared-absorbing filter is produced (by using the above glass plate), a near-infrared-absorbing glass (that is the above glass plate) is attached to one surface of a quartz plate having both surfaces optically polished, and a plate-shaped optical glass that transmits visible light and that has both surfaces optically polished, such as BK-7 (borosilicate optical glass) is attached to the other surface of the quartz plate. While the near-infrared-absorbing filter is constituted to have the above structure, one more plate-shaped optical glass that transmits visible light and that has both surfaces optically polished (e.g., BK-7) may be attached to the other surface of the above plate-shaped optical glass. An optical multi-layered film may be formed on the filter surface as required.
- While a case where the glass block is processed to form a glass plate is explained above, the glass block may be ground and polished to produce a lens or may be processed to produce a product having other form.
- Since the near-infrared-absorbing glass of the present invention has a low glass transition temperature, optical elements such as a lens, a diffraction grating, etc. can be produced therefrom by precision press-molding (mold-shaping) without using any machine-applied processing such as grinding and polishing of their optical-function surfaces. For example, molding surfaces of a known press mold material such as SiC, a carbide material or the like are highly accurately processed so that they have reverse forms of lens surfaces of an aspherical lens, whereby upper and lower mold members are prepared, and a glass preform formed of the near-infrared-absorbing glass of the present invention is heated and precision press-molded with these upper and lower mold members and optionally with a known sleeve or upper and lower mold guide member(s). The forms of the molding surfaces are accurately transferred to the glass in the above manner, whereby an aspherical lens formed of the near-infrared-absorbing glass of the present invention can be produced.
- The thus-obtained aspherical lens is a near-infrared-absorbing element having the function of near infrared absorption and can constitute part or the whole of an optical system for forming an image of an object on a semiconductor image-sensing device, so that the number of optical parts in an image-sensing apparatus can be decreased and that space saving and cost reduction can be realized at the same time.
- Molding surfaces of a press mold material are highly accurately processed so that they have reverse forms of a diffraction grating to prepare upper and lower mold members, and a glass preform is precision press-molded with the above mold in the same manner as in the above-described method, whereby a diffraction grating formed of the near-infrared-absorbing glass of the present invention can be also produced.
- The thus-obtained near-infrared-absorbing element with a diffraction grating works as an optical low-pass filter for light that enters a semiconductor image-sensing device. Since a near-infrared-absorbing filter and an optical low-pass filter can be therefore constituted of one element, the number of optical parts in an image-sensing apparatus can be decreased, and space saving and cost reduction can be realized at the same time.
- In addition, molding surfaces of a press mold material are formed in a reverse form of lens surfaces (e.g., lens surfaces of an aspherical lens) and at the same time processed in a reverse form of grooves of a diffraction grating, and precision press-molding is carried out in the same manner as in the above method, whereby there can be produced a near-infrared-absorbing element that has the function of near infrared absorption, the function of an optical low-pass filter and the function of a lens together.
- A known mold release film may be formed on the molding surface(s) of a press mold as required. Various conditions of the precision press-molding can be determined as required depending upon specifications of an intended near-infrared-absorbing element while applying known conditions.
- By producing near-infrared-absorbing elements according to the above precision press-molding, there can be highly productively produced elements for which mass-production by grinding and polishing is not suitable, such as an aspherical lens, an optical low-pass filter with a diffraction grating, an aspherical lens that functions as an optical low-pass filter and has a diffraction grating, and the like.
- An optical multi-layered film such as an anti-reflection film may be formed on the surface of a near-infrared-absorbing element as required.
- According to the near-infrared-absorbing element of the present invention, the transmittance of visible light is high, and the absorption of near infrared light is large, so that the color sensitivity of a semiconductor image-sensing device can be excellently corrected.
- The present invention also provides an image-sensing apparatus having the above near-infrared-absorbing element and a semiconductor image-sensing device for receiving light that passes through the element and an image-sensing apparatus having a near-infrared-absorbing element produced by the above production process and a semiconductor image-sensing device for receiving light that passes through the element.
- The present invention will be explained more in detail with reference to Examples hereinafter, while the present invention shall not be limited by these Examples.
- Oxide materials including phosphates and fluoride materials were weighed so as to obtain a composition shown in Table 1, and they were mixed and melted in a crucible made of platinum. Glasses in Examples 1 to 6 were melted at 800 to 900° C., and a glass in Comparative Example 1 was melted at 1,300° C.
- Each glass was stirred and refined, and then it was cast on an iron plate to form a block. The glass block was transferred into a furnace, which was pre-heated to a temperature around a glass transition temperature, and annealed to room temperature to give near-infrared-absorbing glasses.
- Samples for measurements were taken from the above-obtained blocks by cutting and measured for various properties as follows. Table 1 shows the results.
- (1) Transmittance Property
- A glass that was polished and had a thickness shown in Table 1 was measured for spectral transmittances at a wavelength of 200 to 1,200 with a spectrophotometer. Table 1 shows a transmittance at each wavelength.
- (2) Thermal Expansion Coefficient
- Measured according to Japan Optical Glass Industry Society Standard JOGIS-08.
- (3) Climate Resistance
- A polished sample was held under conditions including a temperature of 60° C. and a relative humidity of 80% for 1,000 hours and then the surface was observed for an opacification or fogging.
- (4) Transition Temperature (Tg) and sag Temperature (Ts)
- Measured with an apparatus for thermomechanical analysis, supplied by Rigaku Corporation, at a temperature elevation rate of 4° C./minute.
TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 CEx. 1 Glass P cat % 37.0 33.3 42.3 39.5 37.3 35.0 29.0 Composition Al cat % 4.5 2.8 6.9 4.8 4.5 6.5 14.0 Li cat % 23.6 24.8 21.7 18.9 23.8 21.4 24.0 Na cat % 0.0 0.0 0.0 0.0 0.0 0.0 7.0 Mg cat % 7.7 9.8 7.0 8.2 4.7 8.1 3.0 Ca cat % 12.9 10.5 9.2 10.7 13.0 13.0 7.0 Sr cat % 4.1 7.4 6.4 7.5 4.1 4.1 5.0 Ba cat % 6.2 6.6 3.0 6.7 9.2 6.3 4.0 Zn cat % 0.0 0.0 0.0 0.0 0.0 0.0 4.0 Cu cat % 4.0 4.8 3.5 3.8 3.3 5.6 3.0 Total cat % 100.0 100.0 100.0 100.1 99.9 100.0 100.0 Li/R 1.00 1.00 1.00 1.00 1.00 1.00 0.77 Al/P 0.12 0.08 0.16 0.12 0.12 0.19 0.48 (Mg + Ca) 0.67 0.59 0.63 0.57 0.57 0.67 0.43 R′ O an % 65.0 60.0 72.0 67.0 65.0 61.5 60.0 F an % 35.0 40.0 28.0 33.0 35.0 38.5 40.0 Total an % 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Transmittance Measurement mm 0.45 0.30 0.36 0.35 0.40 0.30 0.45 property thickness T400 % 84.5 85.8 85.8 84.0 86.0 84.5 90.0 T500 % 89.0 89.8 89.5 88.8 89.8 89.0 91.0 T600 % 60.0 60.7 60 60 60.2 62.0 60.0 T700 % 7.0 5.0 6.5 6.2 5.2 6.7 8.7 T800 % <1 <1 <1 <1 <1 <1 1.4 T900 % <1 <1 <1 <1 <1 <1 1.4 T1000 % 1.5 1.1 2.0 1.7 1.2 1.9 4.0 T1100 % 5.0 4.5 5.5 5.0 4.0 5.2 10.0 T1200 % 11.5 9.2 12.8 12.0 10.1 12.2 20.5 Glass ° C. 350 325 387 380 340 335 335 transition temperature [Tg] Sag ° C. 390 365 427 420 380 380 380 temperature [Ts] Average linear 160 170 140 150 165 155 170 expansion coefficient at 100-300° C. (×10−7/° C.) Climate resistance NC NC NC NC NC NC NC
Notes:
Ex. = Example,
CEx. = Comparative Example
R = Li + Na + K,
R′ = Mg + Ca + Sr + Ba
NC = No change
Additional notes to Table 1:
1) T400, T500, T600, T700, T800, T1000, T1100 and T1200 stand for transmittances at wavelengths of 400 nm, 500 nm, 600 nm, 700 ma, 800 nm, 1,000 nm, 1,100 nm and 1,200 nm, respectively.
2) Li/R: Li+/(Lii+ + Na+ + K+)
3) Al/P: Al3+/P5+
4) (Mg + Ca)/R′: (Mg2+ + Ca2+)/(Mg2+ + Ca2+ + Sr2+ + Ba2+)
-
FIG. 1 shows spectral transmittances of glasses of Example 1 and Comparative Example 1. Spectral transmittances were obtained when the thickness of each of the glass of Example 1 and the glass of Comparative Example 1 was adjusted such the transmittance at a wavelength of 615 nm was 50%, that is, the glasses of Example 1 and Comparative Example 1 had thicknesses as shown in Table 1. The glass of Example 1 has sufficient transmittance to visible light and sufficient absorption of near infrared light and has a transmittance property that the color sensitivity of a semiconductor image-sensing device can be excellently corrected without forming a near infrared blocking coating. On the other hand, the glass of Comparative Example 1 has low near infrared absorption function, so that its property is that it is desirable to form a near infrared blocking coating for completing the color correction function of a semiconductor image-sensing device. - In the above manner, there were obtained near-infrared-absorbing glasses having a glass transition temperature of less than 400° C., a sag temperature of less than 450° C. and an average linear expansion coefficient, measured at 100 to 300° C., of greater than 130×10−7/° C. but smaller than 180×10−7/° C.
- Plate-shaped glasses formed of glasses having the same compositions as those in Examples 1 to 6 were obtained (molded) by carrying out glass dissolving, refining, homogenizing and mold-casting in the same manner as in Examples 1 to 6. Each plate-shaped glass was sliced and both surfaces of each of the sliced glasses were optically polished to obtain glass plates having predetermined thicknesses. These glass plates were dice-processed to give near-infrared-absorbing glass plates having predetermined thicknesses and sizes. The thickness of each of the glass plates was adjusted such that the transmittance at a wavelength of 615±10 nm was 50% (thicknesses corresponding to measurement thicknesses in Table 1), and each glass plate had a size of 10 mm×10 mm to 30 mm×30 mm. Then, a quartz processed in the form of a plate and two thin-plate glasses formed of an optical glasses (BK-7) each were prepared, and both surfaces of each plate were optically polished. A glass plate formed of a near-infrared-absorbing glass, the quartz plate and two BK-7 thin-plate glasses were stacked in this order while optically polished surfaces thereof were in contact with each other, and an anti-reflection film was provided on each of the outermost surfaces, to produce a near-infrared-absorbing element having the function of a near-infrared-absorbing filter. Images were taken by arranging the above element in front of the light receiving surface of a semiconductor image-sensing device such as CCD, CMOS or the like. Images taken by the above arrangement using the elements of this Example were observed to show that excellent color correction was attained.
- A glass melt was prepared by melting, refining and homogenizing a glass in the same manner as in Examples 1 to 6, and the glass melt was caused to flow down from a nozzle made of platinum. A proper amount of the glass melt was received with a receiving mold and shaped into a spherical glass preform. The thus-shaped preform was once cooled to room temperature and in a non-oxidizing atmosphere containing nitrogen gas or a mixture of nitrogen with hydrogen, the preform was again softened by re-heating and pressed with a press mold. The molding surfaces of the press mold were accurately processed in advance in a reverse form of an intended optical element, and the forms of these molding surfaces were accurately transferred to the glass in the above pressing step. The press-molded product was cooled in the press mold to a temperature at which the glass was not deformed, and then it was taken out from the press mold and annealed. In the above manner, optical elements formed of the glasses of Examples 1 to 6, such as spherical lenses and diffraction gratings, were obtained. Further, an element having a diffraction grating on a lens surface can be also produced by precision press-molding.
- In addition, a spherical glass preform may be produced by preparing a glass block formed of the glass of any one of Example 1 to 6 in the same manner as in Example 7. And, an optical element such as an aspherical lens or a diffraction grating or a near-infrared-absorbing element having a diffraction grating on a surface may be produced by precision press-molding in the same manner as in the above.
- With regard to the form of a lens, there can be produced lenses with various forms such as a convex meniscus form, a concave meniscus form, a biconvex form, a biconcave form, a plano-convex form, a plano-concave form and the like. Preferably, it is arranged that constant near-infrared-absorption can be obtained by equalizing distances of paths of a lens through which light beams going inside a lens pass regardless of distances from the optical axis of the lens. For this purpose, the lens form is preferably a convex meniscus form or a concave meniscus form.
- The near-infrared-absorbing glass of the present invention has excellently high transmittance in a visible light region, an excellent near infrared absorption property, excellent climate resistance, etc., and is suitable for use as/in a near-infrared-absorbing element such as a near-infrared-absorbing filter. Further, the above near-infrared-absorbing filter is particularly suitably used for correcting the color sensitivity of an image-sensing device of CCD, CMOS or the like used in a digital camera or VTR camera.
Claims (14)
1. A near-infrared-absorbing glass comprising, by cationic %, 25 to 45% of P5+, 1 to 10% of Al3+, 15 to 30% of Li+, 0.1 to 10% of Mg2+, 0.1 to 20% of Ca2+, 0.1 to 20% of Sr2+, 0.1 to 20 Ba2+ and 1 to 8% of Cu2+ and comprising, as anionic components, 25 to 50 anionic % of F− and O2−.
2. The near-infrared-absorbing glass of claim 1 , wherein the ratio of the content of Al3+ to the content of P5+ by cationic ratio, Al3+/P5+, is from 0.05 to 0.30.
3. The near-infrared-absorbing glass of claim 1 , wherein the ratio of the total content of Mg2+ and Ca2+ to the total content of Mg2+, Ca2+, Sr2+ and Ba2+ by cationic ratio, (Mg2++Ca2+)/(Mg2++Ca2++Sr2++Ba2+), is from 0.5 to less than 1.0.
4. The near-infrared-absorbing glass of claim 1 , wherein the ratio of the content of Li+ to the total content of Li+, Na+ and K+ by cationic ratio, Li+/(Li++Na+++K+), is from 0.8 to 1.0.
5. The near-infrared-absorbing glass of claim 1 , which has a transmittance property represented by a transmittance of less than 15% at a wavelength of 1,200 nm when it is thickness-adjusted such that it exhibits a transmittance of 50% at a wavelength of 615 nm in a spectral transmittance at a wavelength of 500 to 700 nm.
6. Near-infrared-absorbing glass of claim 5 , which further has the transmittance property represented by
a transmittance of 83% or more at a wavelength of 400 nm,
a transmittance of 88% or more at a wavelength of 500 nm,
a transmittance of 55% or more at a wavelength of 600 nm,
a transmittance of less than 8% at a wavelength of 700 nm,
a transmittance of less than 1% at a wavelength of 800 nm,
a transmittance of less than 1% at a wavelength of 900 nm,
a transmittance of less than 3% at a wavelength of 1,000 nm, and
a transmittance of less than 7% at a wavelength of 1 ,100 nm.
7. A process for the production of the near-infrared-absorbing glass recited in claim 1 , which comprises providing only solid oxides and fluorides as raw materials, heating and melting said raw materials and forming the glass.
8. A near-infrared-absorbing element having the near-infrared-absorbing glass of claim 1 or the near-infrared-absorbing glass produced by the process as described above.
9. The near-infrared-absorbing element of claim 8 , which is a near-infrared-absorbing filter having a glass plate formed of a near-infrared-absorbing glass.
10. The near-infrared-absorbing element of claim 8 , which is an optical low-pass filter.
11. The near-infrared-absorbing element of claim 8 , which is a lens.
12. A process for the production of a near-infrared-absorbing element, which comprises heating and precision press-molding a preform formed of the near-infrared-absorbing glass recited in claim 1 or a near-infrared-absorbing glass produced by the process as described above.
13. An image-sensing apparatus comprising the near-infrared-absorbing element of claim 8 and a semiconductor image-sensing device for receiving light to be transmitted through it.
14. An image-sensing apparatus comprising the near-infrared-absorbing element produced by the process recited in claim 12 and a semiconductor image-sensing device for receiving light to be transmitted through it.
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JP2005-378720 | 2005-12-28 | ||
JP2005378720A JP2007099604A (en) | 2005-09-06 | 2005-12-28 | Near infrared ray absorbing glass, near infrared ray absorbing element provided with the same and imaging device |
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US11/516,047 Abandoned US20070051930A1 (en) | 2005-09-06 | 2006-09-06 | Near-infrared-absorbing glass, near-infrared-absorbing element having the same and image-sensing device |
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US20120165178A1 (en) * | 2010-12-23 | 2012-06-28 | Schott Ag | Fluorophosphate glasses |
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- 2005-12-28 JP JP2005378720A patent/JP2007099604A/en active Pending
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- 2006-08-22 DE DE102006039288A patent/DE102006039288A1/en not_active Ceased
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DE102012103076A1 (en) | 2012-04-10 | 2013-10-10 | Schott Ag | Camera lens with infrared filter and camera module with camera lens |
DE102012103076B4 (en) | 2012-04-10 | 2020-08-06 | Schott Ag | Lens system for a camera module with an infrared filter and camera module with a lens system and method for producing a lens system |
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